Droplet discharging device and method for heating functional liquid thereof

ABSTRACT

A method is for heating a functional liquid of a droplet discharging device that has a storage which houses a container storing a functional liquid containing a functional material; a droplet discharge head discharging the functional liquid in a droplet; a cooling means included to the storage and cooling the functional liquid; and a supply tube supplying the functional liquid that is cooled in the storage to the droplet discharge head. The method includes: heating the functional liquid in the supply tube with waste heat that is generated correspondingly to cooling of the cooling means.

BACKGROUND

1. Technical Field

The present invention relates to a droplet discharging device and amethod for heating a functional liquid of a droplet discharging device.

2. Related Art

Ink-jet devices that discharge a functional liquid in droplets, namelydroplet discharging devices have drawn attention as a device for forminga desired pattern on a substrate. The droplet discharging devices move asubstrate placed on a stage thereof two-dimensionally relative to adroplet discharge head that discharges the functional liquid in dropletsso as to dispose the droplets discharged from the droplet discharge headon predetermined positions of a surface of the substrate, forming apattern.

In the droplet discharging devices, if the viscosity of the functionalliquid is unstable, the droplet weight changes, causing variation of thepattern in size or in shape. Further, when the viscosity of thefunctional liquid is high, a nozzle of the droplet discharge head isclogged, causing a droplet-discharging defect. Therefore, the dropletdischarging devices cool the functional liquid that is to be supplied tothe droplet discharge head by a cooling means or heat it by a heatingmeans so as to control the viscosity of the functional liquid, asdisclosed in JP-A-2000-238281 and JP-A-2005-305973, for example.

A method for forming a wiring pattern on a substrate irradiates thedroplet with a laser beam for high accuracy of wiring width, that is,high accuracy of a diameter of the droplet. The discharged droplet isirradiated with the laser beam to be dried in a short time, being ableto prevent the droplet from spreading after it lands. As the functionalliquid for forming such wiring pattern, a dispersion-based metal inkobtained by dispersing metal particulates of silver (Ag), for example,in a solvent is known.

When the metal ink mentioned above is left at a room temperature, asecondary aggregation or the like occurs in the ink, deteriorating theink. In a case where the droplet discharging devices are drivencontinuously for a long time, the metal ink stored in a tank is kept tobe at the room temperature to deteriorate. Thus a stable operation isdifficult. Therefore, in a case where the metal ink is used, it isnecessary that the tank is cooled by the cooling means so as to cool theink.

On the other hand, if the metal ink that is stored in the tank is cooleddown, the metal ink at a low temperature is supplied from the tank tothe droplet discharge head. As a result, it is difficult for the dropletdischarge head to discharge the ink in droplets because the metal ink isat a low temperature, that is, has high viscosity. This problem can besolved such that the heating means is provided to a supply tube thatcouples the tank and the droplet discharge head so as to heat the metalink flowing in the supply tube. Thus the metal ink that is not used iscooled by the cooling means so as to be prevented from deteriorating andthe metal ink that is in use is heated by the heating means so as todecrease the viscosity thereof.

However, the above structure includes the heating means and the coolingmeans separately, increasing power consumption and causing a larger sizeof the droplet discharging device.

SUMMARY

An advantage of the present invention is to provide a dropletdischarging device and a method for heating a functional liquid of adroplet discharging device that can favorably control a temperature ofthe functional liquid that is to be supplied to a droplet discharge headwhile saving energy.

According to a first aspect of the invention, a method is to heat afunctional liquid of a droplet discharging device having: a storage thathouses a container storing a functional liquid containing a functionalmaterial; a droplet discharge head discharging the functional liquid ina droplet; a cooling means included to the storage and cooling thefunctional liquid; and a supply tube supplying the functional liquidthat is cooled in the storage to the droplet discharge head. The methodincludes: heating the functional liquid in the supply tube with wasteheat that is generated correspondingly to cooling of the cooling means.

According to the method of the first aspect, the functional liquid inthe supply tube is heated by the waste heat generated correspondingly tothe cooling of the cooling means, and then supplied to the dropletdischarge head. Thus, in the method of the first aspect, the functionalliquid that is cooled can be heated without using a heating means formerely heating a functional liquid, being able to achieve energy-saving.

According to a second aspect of the invention, a method is to heat afunctional liquid of a droplet discharging device having: a storage thathouses a container storing a functional liquid containing a functionalmaterial; a droplet discharge head discharging the functional liquid ina droplet; a cooling means included to the storage and cooling thefunctional liquid; and a supply tube supplying the functional liquidthat is cooled in the storage to the droplet discharge head. The methodincludes: heating the functional liquid in the supply tube by heatexchange between the functional liquid in the supply tube; andsurrounding air and assisting the cooling means in cooling with the airthat is cooled by the heat exchange.

According to the method of the second aspect, the surrounding air heatsthe functional liquid in the supply tube by the heat exchange with thefunctional liquid in the supply tube. In addition, the air that iscooled by the heat exchange with the functional liquid assists thecooling means in cooling. Thus, in the method of the second aspect, thefunctional liquid that is cooled can be heated without using a heatingmeans for merely heating a functional liquid and the cooling effect ofthe cooling means can be improved, being able to achieve energy-saving.

According to a third aspect of the invention, a method is to heat afunctional liquid of a droplet discharging device having: a storage thathouses a container storing a functional liquid containing a functionalmaterial; a droplet discharge head discharging the functional liquid ina droplet; a cooling means included to the storage and cooling thefunctional liquid; and a supply tube supplying the functional liquidthat is cooled in the storage to the droplet discharge head. The methodincludes: heating the functional liquid in the supply tube with wasteheat that is generated correspondingly to irradiation of the lightsource.

According to the method of the third aspect, the functional liquid thatis cooled in the supply tube is heated with the waste heat of the lightsource, and then supplied to the droplet discharge head. Thus, in themethod of the third aspect, the functional liquid that is cooled can beheated without using a heating means for merely heating a functionalliquid, being able to achieve energy-saving.

According to a fourth aspect of the invention, a method is to heat afunctional liquid of a droplet discharging device having: a storage thathouses a container storing a functional liquid containing a functionalmaterial; a droplet discharge head discharging the functional liquid ina droplet; a cooling means included to the storage and cooling thefunctional liquid; and a supply tube supplying the functional liquidthat is cooled in the storage to the droplet discharge head. The methodincludes: heating the functional liquid in the supply tube by heatexchange between the functional liquid in the supply tube and arefrigerant in the light source; and assisting in cooling the lightsource with the refrigerant that is cooled by the heat exchange.

According to the method of the fourth aspect, the refrigerant in thelight source heats the functional liquid in the supply tube by the heatexchange with the functional liquid in the supply tube. In addition, therefrigerant that is cooled by the heat exchange with the functionalliquid assists in cooling the light source. Thus, in the method of thefourth aspect, the functional liquid that is cooled can be heatedwithout using a heating means for merely heating a functional liquid andthe cooling effect of the cooling means can be improved, being able toachieve energy-saving.

A droplet discharging device according to a fifth aspect of theinvention includes: a storage that houses a container storing afunctional liquid containing a functional material; a droplet dischargehead discharging the functional liquid in a droplet; a cooling meanscooling the functional liquid that is stored in the container housed inthe storage; a supply tube provided between the container and thedroplet discharge head and supplying the functional liquid stored in thecontainer to the droplet discharge head; and a heating means heating thesupply tube with waste heat that is generated correspondingly to coolingof the cooling means.

According to the droplet discharge device of the fifth aspect, the wasteheat generated correspondingly to the cooling of the cooling means heatsthe functional liquid in the supply tube. Thus, in the device of theaspect, the functional liquid that is cooled can be heated without usinga heating means for merely heating a functional liquid, being able toachieve energy-saving.

In the droplet discharging device of the aspect, the cooling means andthe heating means may be a Peltier element of which a cooling part isthermally brought into contact with the storage so as to cool thefunctional liquid stored in the container and a heat generating part isthermally brought into contact with the supply tube so as to heat thesupply tube.

According to the device of the aspect, one Peltier element can achievecooling the functional liquid in the storage and heating the functionalliquid flowing in the supply tube. Thus the droplet discharge deviceuses the heat given from the Peltier element effectively. Therefore, thedroplet discharge device does not need to be provided with a coolingmeans for cooling a functional liquid and a heating means for heating afunctional liquid separately, being able to reduce the number ofcomponents thereof and achieve natural resource saving, namely befriendly to the environment.

The droplet discharging device of the aspect further includes a blowingmeans provided between the heat generating part and the supply tube andblowing surrounding air to the heat generating part via the supply tube.

According to the device of the aspect, the blowing means promotes theheat exchange between the surrounding air and the functional liquid inthe supply tube so as to heat the functional liquid that is cooled. Inaddition, the blowing means blows the air that is cooled by the heatexchange with the functional liquid to the heat generating part of thePeltier element. This blowing cools the heat generating part, so thatthe Peltier element can improve the cooling effect of the cooling partthereof.

In the droplet discharging device of the aspect, the cooling means andthe heating means may be a heat pump of which a cooling part isthermally brought into contact with the storage so as to cool thefunctional liquid stored in the container and a heat generating part isthermally brought into contact with the supply tube so as to heat thesupply tube.

According to the device of the aspect, the heat pump cools thefunctional liquid that is in the storage and heats the functional liquidthat is in the supply tube. Thus the droplet discharge device uses theheat given from the heat pump effectively. Therefore, the dropletdischarge device does not need to be provided with a cooling means forcooling a functional liquid and a heating means for heating a functionalliquid separately, being able to reduce the number of components thereofand achieve natural resource saving, namely be friendly to theenvironment.

A droplet discharging device according to a sixth aspect of theinvention includes: a storage that houses a container storing afunctional liquid containing a functional material; a droplet dischargehead discharging the functional liquid in a droplet to an object; acooling means cooling the functional liquid that is stored in thecontainer housed in the storage; a supply tube provided between thecontainer and the droplet discharge head and supplying the functionalliquid stored in the container to the droplet discharge head; a lightsource irradiating an area of the object on which the droplet lands withlight; and a heating means heating the supply tube with waste heat thatis generated by irradiation of the light source.

According to the device of the sixth aspect, the functional liquid thatis to be supplied to the droplet discharge head is warmed with the wasteheat of the light source. Thus the droplet discharging device does notneed a heating means for merely heating a functional liquid, being ableto achieve energy-saving and natural resource saving. Accordingly, thedevice being environmental-friendly can be provided.

In the device of the aspect, the heating means may include a circulationpump and a heat exchanger; the circulation pump may allow a refrigerantto circulate between a case of the light source and the heat exchanger;and the heat exchanger may provide heat of the case to the functionalliquid that is in the supply tube by heat exchange between therefrigerant and the supply tube.

According to the device of the aspect, the refrigerant circulatesthrough the case of the light source to be heated and is sent to theinside of the heat exchanger. The refrigerant that is sent to the heatexchanger is cooled by the heat exchange with the functional liquid thatis supplied from the storage. Then the refrigerant that is cooled issent to the case of the light source so as to cool the light sourceeffectively. Thus the droplet discharging device does not need a heatingmeans for merely heating a functional liquid and a cooling means formerely cooling a light source, being able to achieve energy-saving andnatural resource saving. Accordingly, the device beingenvironmental-friendly can be provided.

In the device of the aspect, the circulation pump may include a coolingmechanism and circulate the refrigerant that is cooled with the coolingmechanism to the case of the light source.

According to the device, the cooling mechanism of the circulation pumpimproves the cooling effect of the light source.

In the device of the aspect, the heating means may be a cooling fan thatsucks external air to an inside of the case of the light source andblows inner air of the case to the supply tube that is provided outsideof the case.

According to the device of the aspect, the functional liquid that is tobe supplied to the droplet discharge head is warmed with the waste heatexhausted from the light source. Thus the device does not need aparticular heating means, being able to achieve energy-saving andnatural resource saving. Accordingly, the device beingenvironmental-friendly can be provided.

A droplet discharging device according to a seventh aspect of theinvention includes: a storage that houses a container storing afunctional liquid containing a functional material; a droplet dischargehead discharging the functional liquid in a droplet; a cooling meanscooling the functional liquid that is stored in the container housed inthe storage; a supply tube that is provided between the container andthe droplet discharge head, supplies the functional liquid stored in thecontainer to the droplet discharge head, is wound around outer peripheryof the storage, and heats the functional liquid therein by heat exchangewith surrounding air.

According to the device of the seventh aspect, the supply tube increasesthe distance from the container to the droplet discharge head, that is,a chance of the heat exchange between the functional liquid and thesurrounding air. In addition, the supply tube allows the functionalliquid to absorb the heat energy of the surrounding air of the storage,being able to improve the heat insulating effect in the storage andachieve energy-saving.

In the device of the aspect, the supply tube may be multiply-woundaround the periphery of the storage such that an upstream side of thefunctional liquid is disposed at an inner winding and a downstream sideof the functional liquid is disposed at an outer winding.

According to the droplet discharging device of the aspect, thefunctional liquid that is cooled goes around the inner winding and thefunctional liquid that is to be supplied to the droplet discharge headgoes around the outer winding. Therefore, the droplet discharging devicecan further improve the heat insulating effect in the storage andachieve energy-saving.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a whole perspective view showing a droplet discharging deviceaccording to a first embodiment of the invention.

FIG. 2 is a schematic view showing a state of discharging a droplet froma droplet discharge head to a green sheet according to the firstembodiment of the invention.

FIG. 3 is an explanatory diagram showing an arrangement of nozzles ofthe droplet discharge head according to the first embodiment of theinvention.

FIG. 4 is a sectional view showing a major structure of a pack storagehousing an ink-pack according to the first embodiment of the invention.

FIG. 5 is an electric block circuit diagram for explaining an electricalstructure of the droplet discharging device according to the firstembodiment of the invention.

FIG. 6 is a whole perspective view showing a droplet discharging deviceaccording to a second embodiment of the invention.

FIG. 7 is a schematic view showing an arrangement of droplet dischargeheads according to the second embodiment of the invention.

FIG. 8 is a schematic view for explaining a heat exchange system and acirculation system of cooling water according to the second embodimentof the invention.

FIG. 9 is an electric block circuit diagram for explaining an electricalstructure of the droplet discharging device according to the secondembodiment of the invention.

FIG. 10 is a sectional view showing a major structure of a pack storageaccording to a modification of the invention.

FIG. 11 is a sectional view showing a major structure of a pack storageaccording to a modification of the invention.

FIG. 12 is a schematic view showing a heat exchange system according toa modification of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

A droplet discharging device by which a wiring pattern is formed on agreen sheet according to a first embodiment of the invention will now bedescribed with reference to FIGS. 1 to 5.

FIG. 1 is a whole perspective view for explaining a droplet dischargingdevice 10. This droplet discharging device 10 includes a rectangularparallelepiped base 11. On an upper surface of the base 11, a pair ofguide grooves 12 extending in a longitudinal direction of the base 11(hereinafter, referred to as merely “Y-arrow direction”) is provided.Above the guide grooves 12, a stage 13 that moves in Y-arrow directionand reverse Y-arrow direction along the guide grooves 12 is provided. Onan upper surface of the stage 13, a placing part 14 is formed. Theplacing part 14 places a low temperature firing substrate before fired(hereinafter, referred to as merely “green sheet S”) thereon. Theplacing part 14 positions and fixes the green sheet S with respect tothe stage 13 so as to convey the green sheet S in Y-arrow direction andreverse Y-arrow direction. On the upper surface of the stage 13, arubber heater H is provided. The rubber heater H heats the whole uppersurface of the green sheet S that is placed on the placing part 14 up toa predetermined temperature. In the embodiment, the green sheet S is thelow temperature firing substrate having flexibility. The green sheet Sis obtained such that powder of glass ceramic based material and adispersion medium are mixed with a binder, a foam stabilizer, and thelike so as to make slurry, and the slurry is shaped in plate and dried.

The base 11 is provided with a guiding member 15 having a shape of agate and straddling the base 11 in a direction perpendicular to Y-arrowdirection. On the guiding member 15, a pack storage 16 extending inX-arrow direction is provided. In the pack storage 16, an ink-pack 33(see FIG. 4) as a container storing a meal ink F (see FIG. 2) as afunctional liquid is housed. The metal ink F stored in the ink pack 33is supplied through a supply tube T as a supply pipe connected with theink pack 33 to a droplet discharge head (hereinafter, referred to asmerely “discharge head”) 20 at predetermined pressure. The metal ink Fsupplied to the discharge head 20 is discharged to the green sheet S asa droplet Fb (see FIG. 2).

The metal ink F can be a dispersion based metal ink obtained bydispersing metal particles as a functional material, such as metalparticulates as a functional material having several nm diameter, in asolvent. The metal ink F exhibits its function (conductivity in theembodiment) when it is dried.

Examples of the metal particulates for the metal ink F includes gold(Au), silver (Ag), copper (Cu), aluminum (Al), palladium (Pd), manganese(Mn), titanium (Ti), tantalum (Ta), nickel (Ni), oxide products ofthese, and particulates of superconductor. The diameter of the metalparticulates is preferably in the range from 1 nm to 0.1 μm. The metalparticulates having more than 0.1 μm diameter sometimes clogs a nozzle Nof the discharge head 20. While, particulates having less than 1 nmdiameter sometimes make a volume ratio of the dispersing agent withrespect to the metal particulates so large that the ratio of the organicmatter in a film that is to be obtained becomes excessive.

Here, any dispersion medium that is capable of dispersing theabove-described metal particulates and does not cause an aggregation canbe used. Examples of the dispersion medium may include: aqueoussolvents; alcohols such as methanol, ethanol, propanol, and butanol;hydro-carbon compounds such as n-heptane, n-octane, decane, dodecane,tetradecane, toluene, xylene, cymene, durene, indene, dipentene,tetrahydronaphthalene, decahydronaphthalene, and cyclohexylbenzene;polyols such as ethylene glycol, diethylene glycol, triethylene glycol,glycerin, and 1,3-propanediol; ether compounds such as polyethyleneglycol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether,ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether,diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether,1,2-dimethoxyethane, bis (2-methoxyethyl) ether, and p-dioxane; andpolar compounds such as propylene carbonate, gamma-butyrolactone,N-methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide,cyclohexanone, and ethyl lactate. Water, alcohols, hydro-carboncompounds, and ether compounds are preferably used in terms ofparticulate dispersibility, dispersion-liquid stability, andapplicability to droplet discharge. Water and hydro-carbon compounds areused more preferably.

For example, such metal ink F can be used that is obtained by dispersingsilver (Ag) particles in an aqueous solvent containing 40% of water(boiling point: 100° C.), 40% of ethylene glycol (boiling point: 198°C.), and 30% of polyethylene glycol #1000 (decomposition temperature:168° C.). In addition, such metal ink F can also be used that isobtained by dispersing metal particulates (particles of Au, Ag, Ni, Mn,and the like) in a solvent containing tetradecane (boiling point: 253°C.).

When the droplet Fb of the metal ink F is heated, part of the solvent orthe dispersion medium of the ink is evaporated from a surface of thedroplet, increasing the viscosity of its exterior surface. Namely, solidcontent (particle) concentration at the periphery of the droplet Fbbecomes saturated faster than that at the central part of the droplet,increasing the viscosity of the droplet from its exterior surface. Theviscosity increases at the exterior surface of the droplet Fb, so thatthe droplet Fb of the metal ink F is prevented from spreading in asurface direction of the green sheet S, namely is subjected to pinning.

The guiding member 15 is provided with a pair of upper and lower guiderails 18 extending along X-arrow direction at approximate whole width ofthe guiding member 15. On the pair of upper and lower guide rails 18, acarriage 19 is attached. The carriage 19 moves in X-arrow direction andreverse X-arrow direction by being guided along the guide rails 18. Thecarriage 19 includes the droplet discharge head 20.

As shown in FIG. 2, the droplet discharge head 20 is provided with anozzle plate 21 at the bottom side thereof. The nozzle plate 21 has thebottom surface (hereinafter, referred to as merely “nozzle formingsurface 21 a”) that is approximately parallel to the upper surface ofthe green sheet S (hereinafter, referred to as merely “discharge surfaceSa”). When the green sheet S is positioned directly under the dischargehead 20, a distance between the nozzle forming surface 21 a of thenozzle plate 21 and the discharge surface Sa, that is a platen gap, ismaintained at a predetermined distance (for example, 500 μm).

In FIG. 3, the nozzle forming surface 21 a is provided with a pair ofnozzle rows NL composed of a plurality of nozzles N arranged alongX-arrow direction. Each nozzle row of the pair of nozzle rows NL has 180nozzles N in every inch. FIG. 3 shows 10 nozzles N in each row for thesake of convenience of explanation.

In the pair of nozzle rows NL, each nozzle N included to one nozzle rowNL fills each gap between the nozzles N included to the other nozzle rowNL when they are viewed in Y-arrow direction. Namely, the discharge head20 includes 180 nozzles N at each row, that is, 360 nozzles N at both ofthe rows in every inch in X-arrow direction. Namely, the maximumresolution in X-arrow direction is 360 dpi.

In FIG. 2, a supply tube T is connected to the upper side of thedischarge head 20. The supply tube T is formed to extend in Z-arrowdirection, and supplies the metal ink F from the ink pack 33 housed inthe pack storage 16 to the discharge head 20.

On the upper side of each of the nozzles N, a cavity 22 communicatingwith the supply tube T is formed. The cavity 22 stores the metal ink Fsupplied from the supply tube T and supplies part of the metal ink Fwhich is stored therein to the nozzle N which is communicated therewith.On the upper side of the cavity 22, a vibration plate 23 is provided.The vibration plate 23 vibrates along Z-arrow direction so as toincrease and decrease the volume of the cavity 22. On the upper side ofthe vibration plate 23, a piezoelectric element PZ is provided for everynozzle N. The piezoelectric element PZ stretches and constricts alongZ-arrow direction so as to vibrate the vibration plate 23 along Z-arrowdirection. Vibration of the vibration plate 23 along Z-arrow directionallows the metal ink F to be discharged from the nozzle N in thedroplets Fb having a predetermined size. The droplets Fb that aredischarged from the nozzle N travel toward reverse Z-arrow direction andthen land on the discharge surface Sa of the green sheet S.

The pack storage 16 will now be described with reference to FIG. 4. FIG.4 shows a section of a major structure of the pack storage 16.

Referring to FIG. 4, a side wall at a front side of the pack storage 16,that is, at reverse Y-arrow direction is a heat conducting plate 32 madeof stainless, for example. Further, each side wall other than the sidewall at the front side of the pack storage 16 is made of heat insulatingmaterial 31. The ink pack 33 that stores the metal ink F is housed in aspace surrounded by these heat insulating materials 31 and the heatconducting plate 32. The ink pack 33 contacts an inner surface of theheat conducting plate 32.

The ink pack 33 housed in the pack storage 16 is coupled through thesupply tube T to the discharge head 20. The ink pack 33 supplies thecavity 22 with the metal ink F through the supply tube T. The inside ofthe pack storage 16 is coupled through a suction tube (not shown) to asuction pump VP (see FIG. 5). The suction pump VP sucks the inside ofthe pack storage 16 so as to produce a negative pressure there. Thesuction pump VP adjusts the negative pressure of the inside of the packstorage 16 so as to adjust pressure that is to be given to the ink pack33. Thus the supply quantity of the metal ink F is adjusted.

To an outer surface of the heat conducting plate 32, a Peltier elementPT as a cooling means or a heating means is attached. The Peltierelement PT contacts the outer surface of the heat conducting plate 32 ata cooling part PTa thereof. The cooling part PTa of the Peltier elementPT cools down the inside of the pack storage 16 via the heat conductingplate 32. This cooling cools down the metal ink F in the ink pack 33provided to the inside of the pack storage 16. The cooling part PTa ofthe Peltier element PT cools the metal ink F in the ink pack 33 down to5 degrees Celsius in the embodiment. This cooling can suppress thesecondary aggregation of the metal particulates, namely can prevent thedeterioration of the ink F.

At a heat generating part PTb of the Peltier element PT, a blower 34 isprovided. The blower 34 rotates a fan (not shown) by a fan motor MF (seeFIG. 5) to suck the surrounding air A. Then the blower 34 blows the airA which is sucked to the heat generating part PTb of the Peltier elementPT. The supply tube T contacts a suction side of the blower 34.

Accordingly, the metal ink F that is cooled in the ink pack 33 housed inthe pack storage 16 carries out the heat exchange with the air A suckedby the blower 34 along the way being supplied through the supply tube Tto the discharge head 20. Namely, the air A at the common temperature(20 degrees Celsius) hits the supply tube T when the air A is sucked bythe blower 34. At this time, the air A at the common temperatureincreases heat quantity of the metal ink F that flows in the supply tubeT and is at 5 degrees Celsius, warming the metal ink F. Consequently,the metal ink F warmed by the heat exchange is supplied to the dischargehead 20.

On the other hand, the air A that is sucked by the blower 34 is cooledby the heat exchange with the metal ink F. The air A that is cooled isblown to the heat generating part PTb of the Peltier element PT by theblower 34. This blowing cools the heat generating part PTb, so that thePeltier element PT can improve the cooling effect of the cooling partPTa thereof.

An electrical structure of the droplet discharging device 10 structuredas above will now be described with reference to FIG. 5.

In FIG. 5, a controller 50 includes CPU 50A, ROM 50B, and RAM 50C. Thecontroller 50 carries out a conveying process of the stage 13, aconveying process of the carriage 19, a droplet discharging process ofthe discharge head 20, a heating process of the rubber heater H, a drivecontrol of the Peltier element PT, a drive control of the blower 34, andthe like in accordance with various data and various control programsthat are stored therein.

To the controller 50, an input/output device 51 having various operationswitches and displays is coupled. The input/output device 51 displays aprocessing state of each process which is carried out by the dropletdischarging device 10. The input/output device 51 produces bitmap dataBD for forming a pattern by the droplet Fb on the green sheet S andinputs the bitmap data BD to the controller 50.

The bitmap data BD is data defining “on” or “off” of each piezoelectricelement PZ in accordance with a value (0 or 1) of each bit. The bitmapdata BD is data defining whether the droplet Fb is discharged or not oneach position of a drawing plane surface (discharge surface Sa) abovewhich the discharge head 20, namely each nozzle N, passes through. Inother words, the bitmap data BD is data for discharging the droplet Fbon a desired forming position of a pattern defined on the dischargesurface Sa.

To the controller 50, an X-axis motor driving circuit 52 is coupled. Thecontroller 50 outputs a driving control signal to the X-axis motordriving circuit 52. The X-axis motor driving circuit 52 responds to thedriving control signal received from the controller 50 to normally orreversely rotate an X-axis motor MX for conveying the carriage 19.

To the controller 50, a Y-axis motor driving circuit 53 is coupled. Thecontroller 50 outputs a driving control signal to the Y-axis motordriving circuit 53. The Y-axis motor driving circuit 53 responds to thedriving control signal received from the controller 50 to normally orreversely rotate a Y-axis motor MY for conveying the stage 13.

To the controller 50, a head driving circuit 54 is coupled. Thecontroller 50 produces a discharge timing signal LT synchronized with apredetermined discharge frequency so as to output it to the drivingcircuit 54. The controller 50 synchronizes a driving voltage COM fordriving each of piezoelectric elements PZ with the discharge frequencyso as to output it to the head driving circuit 54.

The controller 50 produces a pattern forming control signal SI fordriving each of the piezoelectric elements PZ according to the desiredpattern forming position, based on the bitmap data BD so as to seriallytransfer the pattern forming control signal SI to the head drivingcircuit 54. The head driving circuit 54 sequentially serial/parallelconverts the pattern forming control signal SI received from thecontroller 50 in accordance with each of the piezoelectric elements PZ.Whenever the head driving circuit 54 receives the discharge timingsignal LT outputted from the controller 50, the head driving circuit 54latches the pattern forming control signal SI, which is serial/parallelconverted, to supply the driving voltage COM to the piezoelectricelement PZ selected by the pattern forming control signal SI.

To the controller 50, a rubber heater driving circuit 55 is coupled. Thecontroller 50 outputs a driving control signal to the rubber heaterdriving circuit 55. The rubber heater driving circuit 55 responds to thedriving control signal received from the controller 50 to drive therubber heater H, controlling the temperature of the green sheet S placedon the stage 13 to a predetermined temperature. The predeterminedtemperature of the green sheet S is 46 degrees Celsius in theembodiment. Thus the green sheet S increases the drying speed of thedroplet Fb that lands thereon.

To the controller 50, a Peltier element driving circuit 56 is coupled.The controller 50 outputs a driving control signal to the Peltierelement driving circuit 56. The Peltier element driving circuit 56responds to the driving control signal received from the controller 50to drive a Peltier element PT. The Peltier element PT attached to theheat conducting plate 32 of the pack storage 16 cools the inside of thepack storage 6 down to 5 degrees Celsius. Namely, the cooling by thePeltier element PT cools the metal ink F in the ink pack 33 housed inthe pack storage 16 down to 5 degrees Celsius, preventing the ink fromdeteriorating.

To the controller 50, a fan motor driving circuit 57 is coupled. Thecontroller 50 outputs a driving control signal to the fan motor drivingcircuit 57. The fan motor driving circuit 57 responds to the drivingcontrol signal received from the controller 50 to drive a fan motor MFthat rotates a fan of the blower 34. If the fan motor MF is driven torotate the fan, the blower 34 sucks the air A which is at a commontemperature and is at the circumference of the droplet dischargingdevice 10 via the supply tube T. Then the blower 34 blows the air Awhich is sucked to the heat generating part PTb of the Peltier elementPT. Accordingly, when the air A positively flows toward the blower 34,the heat exchange is carried out between the air A and the supply tubeT. Thus the supply tube T is warmed to warm the metal ink F thereinside.On the other hand, the air A which flows toward the blower 34 is cooledby the metal ink F, thereby effectively cooling down the heat generatingpart PTb of the Peltier element PT.

To the controller 50, a negative-pressure generating pump drivingcircuit 58 is coupled. The controller 50 outputs a driving controlsignal to the negative-pressure generating pump driving circuit 58. Thenegative-pressure generating pump driving circuit 58 responds to thedriving control signal received from the controller 50 to drive thesuction pump VP, producing a predetermined negative pressure in theinside of the pack storage 16. The suction pump VP adjusts the negativepressure of the inside of the pack storage 16, so that the innerpressure of the ink pack 33 is adjusted, adjusting the supply quantityof the metal ink F.

Next, operations of the droplet discharging device 10 will now bedescribed.

As shown in FIG. 1, the green sheet S is placed on the stage 13 suchthat the discharge surface Sa is arranged on the upper side. At thistime, the stage 13 is disposed at the reverse Y-arrow direction side inrelation to the carriage 19.

At this state, the controller 50 receives the bitmap data BD for forminga wiring pattern by the droplet Fb, from the input/output device 51. Thecontroller 50 stores the bitmap data BD received from the input/outputdevice 51.

The controller 50 drives the rubber heater H via the rubber heaterdriving circuit 55 so as to evenly control the temperature of the wholegreen sheet S placed on the stage 13 at a predetermined temperature.

The controller 50 drives the Peltier element PT via the Peltier elementdriving circuit 56 so as to cool the metal ink F in the ink pack 33housed in the pack storage 16 down to 5 degrees Celsius. The controller50 drives the fan motor MF via the fan motor driving circuit 57 so as tosuck the air A which is at a common temperature and at the circumferenceof the droplet discharging device 10 via the fan motor driving circuit57. Then the air A which is sucked is blown to the heat generating partPTb of the Peltier element PT. Then the controller 50 warms the metalink F which is cooled down to 5 degrees Celsius by the heat exchangebetween the air A and the metal ink F so as to supply the metal ink F tothe discharge head 20.

After that, the controller 50 drives the X-axis motor MX via the X-axismotor driving circuit 52 so as to move the discharge head 20 such thatthe green sheet S passes directly under the discharge head 20 in theY-arrow direction. Then the controller 50 drives the Y-axis motor MY viathe Y-axis driving circuit 53 so as to start moving (moving forth) thestage 13.

Once the controller 50 starts the moving (moving forth) of the stage 13,the controller 50 produces the pattern forming control signal SI basedon the bitmap data BD to output the pattern forming control signal SIand the driving voltage COM to the head driving circuit 54. Namely, thecontroller 50 drives each of the piezoelectric elements PZ via the headdriving circuit 54 so as to discharge the droplet Fb from the nozzle Nwhich is selected, every time the desired pattern forming positionpasses directly under the discharge head 20. The droplet Fb which landson the green sheet S is dried shortly after the landing because thegreen sheet S is heated. Thus the wiring pattern is formed on the greensheet S.

Here, advantageous effects of the first embodiment will be describedbelow.

(1) According to the embodiment, the Peltier element PT is mounted onthe heat conducting plate 32 of the pack storage 16. The Peltier elementPT cools the inside of the pack storage 16 to cool the metal ink F inthe ink pack 33 that is housed in the storage 16 down to a temperature(5 degrees Celsius) at which the ink does not cause an aggregationconstantly. Therefore, the metal ink F stored in the ink pack 33 doesnot deteriorate.

(2) According to the embodiment, the blower 34 is mounted at the heatgenerating part PTb of the Peltier element PT and contacts the supplytube T at the suction side thereof. The blower 34 actively allows thesurrounding air A which is at a common temperature to contact the supplytube T, and sucks the air A. Then the blower 34 blows the air A which issucked to the heat generating part PTb of the Peltier element PT.

Namely, the surrounding air A which is warm as being at the commontemperature carries out the heat exchange with the supply tube T,heating the metal ink F flowing in the supply tube T. Thus the metal inkF which is cooled down to 5 degrees Celsius is warmed by the air A so asto be supplied to the discharge head 20 with low viscosity. Accordingly,the clogging of the nozzle N of the droplet discharge head 20 isprevented from occurring.

Further, in the embodiment, since the metal ink F is warmed by the heatenergy of the surrounding air A, the heating means for merely heatingthe metal ink F is not needed. Thus energy saving can be achieved in thepattern forming. Further, since the number of components can bedecreased, the droplet discharging device 10 can be formed small in size(achieve space saving) and achieve natural resource saving, namely befriendly to the environment.

(3) According to the embodiment, the air which is cooled by the heatexchange with the metal ink F cools the heat generating part PTb of thePeltier element PT. Namely, the cooling of the heat generating part PTbof the Peltier element PT can increase the cooling effect of the coolingpart PTa, being able to decrease the power consumption (achieve energysaving) of the Peltier element PT.

Second Embodiment

A second embodiment of the invention will be described below withreference to FIGS. 6 to 9. A structure of the second embodiment includesa laser device adding to the structure of the first embodiment. In thesecond embodiment, the alteration is mainly described in detail.Elements that are common to the first embodiment are indicated by thesame reference numerals.

In FIG. 6, the pack storage 16 includes the Peltier element PT as acooling means so as to cool the metal ink F stored therein down to 5degrees Celsius. The metal ink F is supplied to the discharge head 20through the supply tube T that is coupled to the pack storage 16. Thesupply tube T couples the pack storage 16 with the discharge head 20 ina manner passing through a heat exchanger 40. The metal ink F that iscooled in the pack storage 16 is warmed when it passes through the heatexchanger 40, and then is supplied to the discharge head 20. The metalink F supplied to the discharge head 20 is discharged to the green sheetS in droplets Fb from the discharge head 20.

FIG. 7 is a schematic view showing two discharge heads 20 mounted on thecarriage 19 viewed from the green sheet S side (from the bottom side).The two discharged heads 20 are arranged in Y-arrow direction. The twodischarge heads 20 are arranged to be overlapped partially when viewedfrom Y-arrow direction and be in parallel to each other along X-arrowdirection.

Referring to FIG. 8, in a case 19 a of the carriage 19, a space holdingmember 43 connects a lower supporting plate 41 and an upper supportingplate 42. To the lower supporting plate 41, the two discharge heads 20are fixed. To the upper supporting plate 42, a first semiconductor laserdevice LD1 and a second semiconductor laser device LD2 as light sourcesare respectively fixed.

Each of the first semiconductor laser device LD1 and the secondsemiconductor laser device LD2 includes a rectangular parallelepipedcase K that is formed long in X-arrow direction. The case K of the firstsemiconductor laser device LD1 is arranged at a position that is morereverse Y-arrow direction in relation to the two discharge heads 20 inthe coordinate space of Y-arrow direction. The case K of the secondsemiconductor laser device LD2 is arranged at a position that is moreY-arrow direction in relation to the two discharge heads 20 in thecoordinate space of Y-arrow direction.

Each of the case K of the first semiconductor laser device LD1 and thecase K of the second semiconductor laser device LD2 includes the samenumber of semiconductor lasers LS (see FIG. 9) as the number of thenozzles N included to each of the two discharge heads 20. Further, eachof the case K of the first semiconductor laser device LD1 and the case Kof the second semiconductor laser device LD2 respectively includes alaser driving circuit 60 (see FIG. 9) for driving each of thesemiconductor lasers LS.

The semiconductor lasers LS respectively emit laser light L toward thedischarge surface Sa. The laser light L emitted from the firstsemiconductor laser device LD1 passes through through-holes 42 a and 41a that are respectively formed on the upper supporting plate 42 and thelower supporting plate 41 to be sent toward reverse Y-arrow direction inrelation to each of the nozzles N. Further, the laser light L emittedfrom the second semiconductor laser device LD2 passes throughthrough-holes 42 a and 41 a that are respectively formed on the uppersupporting plate 42 and the lower supporting plate 41 to be sent towardY-arrow direction in relation to each of the nozzles N.

Namely, the laser light L emitted from the first semiconductor laserdevice LD1 irradiates the droplets Fb that are discharged from each ofnozzles N when the droplets Fb are at the reverse Y-arrow direction inrelation to the nozzles N. The laser light L emitted from the secondsemiconductor laser device LD2 irradiates the droplets Fb that aredischarged from each of the nozzles N when the droplets Fb are at theY-arrow direction in relation to the nozzles N.

When the stage 13 moves toward reverse Y-arrow direction and thedroplets Fb are discharged from the nozzles N of the discharge heads 20,the laser light L emitted from the first semiconductor laser device LD1irradiates the droplets Fb that land on the green sheet S. On the otherhand, when the stage 13 moves toward Y-arrow direction and the dropletsFb are discharged from the nozzles N of the discharge heads 20, thelaser light L emitted from the second semiconductor laser device LD2irradiates the droplets Fb that land on the green sheet S. The laserlight L applied to the droplets Fb heats and helps the droplets Fb bedried by energy thereof.

In FIG. 8, a side wall at the back side of the pack storage 16 is a heatconducting plate made of, for example, stainless. Each side wall otherthan the one at the back side of the pack storage 16 is made of heatinsulating material. In a space surrounded by these heat insulatingmaterial and a heat conducting plate, an ink pack 33 that stores themetal ink F is housed, as shown in dashed line in FIG. 8. The ink pack33 contacts an inner surface of the heat conducting plate. The Peltierelement PT cools the inside of the pack storage 16 at the cooling partthereof via the heat conducting plate, namely cools the metal ink F inthe ink pack 33. The Peltier element PT cools the metal ink F in the inkpack 33 down to 5 degrees Celsius in the embodiment. This coolingsuppresses the secondary aggregation of the metal particulates toprevent the deterioration of the metal ink F.

The supply tube T is a flexible tube made of synthetic resin andincludes a stainless pipe Ta at a portion passing through the inside ofthe heat exchanger 40. The stainless pipe Ta raises the efficiency ofthe heat exchange between cooling water W as a refrigerant filling theheat exchanger 40 and the metal ink F which flows in the stainless pipeTa, warming the metal ink F that flows in the supply tube T.

To the front side of the heat exchanger 40, a circulation pump VPC isprovided. The circulation pump VPC pumps up the cooling water W that isin the heat exchanger 40 through a suction tube T1. The circulation pumpVPC allows the cooling water W which is pumped up thereby to go througha lead out tube T2 around each of the lasers LS of the firstsemiconductor laser device LD1 and each of the lasers LS of the secondsemiconductor laser device LD2 and then return to the heat exchanger 40.

The cooling water W to be returned to the heat exchanger 40 receivesheat from each of the semiconductor lasers LS and from circuit elementsmounted on the laser driving circuit 60 so as to be warmed. The heat ofthe cooling water W that is warmed is given to the metal ink F in theheat exchanger 40. Namely, the cooling water W that is warmed is cooledby the heat exchange with the metal ink F. The cooling water W that iscooled in the heat exchanger 40 is pumped up by the circulation pump VPCagain to be sent to the first semiconductor laser device LD1 and thesecond semiconductor laser device LD2. Thus, the insides of the firstsemiconductor laser device LD1 and the second semiconductor laser deviceLD2 are cooled.

The circulation pump VPC has a cooling mechanism. The cooling water Wthat is pumped up is cooled further in the circulation pump VPC to besent to the first semiconductor laser device LD1 and the secondsemiconductor laser device LD2. As a result, the insides of the firstsemiconductor laser device LD1 and the second semiconductor laser deviceLD2 are further effectively cooled.

An electrical structure of the droplet discharging device 10 structuredas above will now be described with reference to FIG. 9. The controller50 carries out a conveying process of the stage 13, a conveying processof the carriage 19, and a droplet discharging process of the dischargehead 20 in accordance with various data and various control programsthat are stored therein. In addition, the controller 50 also carries outan irradiation process of the first semiconductor laser device LD1 andthe second semiconductor laser device LD2, a cooling process of thePeltier element PT, a suction process of the suction pump VP, acirculation process of the circulation pump VPC, and the like.

To the controller 50, a circulation pump driving circuit 59 is coupled.The controller 50 outputs a driving control signal to the circulationpump driving circuit 59. The circulation pump driving circuit 59responds to the driving control signal received from the controller 50to drive the circulation pump VPC. The driving of the circulation pumpVPC allows the cooling water W therein to go around a closed loopcomposed of the tubes T1, T2, the circulation pump VPC, the firstsemiconductor laser device LD1, the second semiconductor laser deviceLD2, and the heat exchanger 40.

To the controller 50, a laser driving circuit 60 is coupled. As is thecase with the head driving circuit 54, the controller 50 produces anirradiation timing signal LTb synchronized with a predeterminedirradiation frequency so as to output it to the laser driving circuit60. The controller 50 selects either the first semiconductor laserdevice LD1 or the second semiconductor laser device LD2. The controller50 produces a driving voltage COMb synchronized with the irradiationfrequency so as to output it to the laser driving circuit 60. Thedriving voltage COMb is used for allowing each of the semiconductorlasers LS of the semiconductor laser device that is selected to emit thelaser light L.

When the stage 13 moves toward reverse Y-arrow direction to form apattern, the controller 50 selects the first semiconductor laser deviceLD1 and outputs the driving voltage COMb, which is used for allowingeach of the semiconductor lasers LS of the first semiconductor laserdevice LD1 to emit the laser light L, to the laser driving circuit 60.On the other hand, when the stage 13 moves toward Y-arrow direction toform a pattern, the controller 50 selects the second semiconductor laserdevice LD2 and outputs the driving voltage COMb, which is used forallowing each of the semiconductor lasers LS of the second semiconductorlaser device LD2 to emit the laser light L, to the laser driving circuit60.

The controller 50 produces a pattern forming control signal SIb fordriving each of the semiconductor lasers LS in accordance with thedesired pattern forming position, based on the bitmap data BD so as toserially transfer the pattern forming control signal SIb to the drivingcircuit 60. The laser driving circuit 60 sequentially serial/parallelconverts the pattern forming control signal SIb received from thecontroller 50 with respect to each of the semiconductor lasers LS.Whenever the laser driving circuit 60 receives the irradiation timingsignal LTb outputted from the controller 50, the laser driving circuit60 latches the pattern forming control signal Sib that isserial/parallel converted so as to supply the semiconductor lasers LSselected by the pattern forming control signal SIb with the drivingvoltage COMb.

Next, operations of the droplet discharging device 10 will now bedescribed.

As shown in FIG. 6, the green sheet S is placed on the stage 13 suchthat the discharge surface Sa is arranged on the upper side. At thistime, the green sheet S placed on the stage 13 is disposed at thereverse Y-arrow direction side in relation to the carriage 19.

At this state, the controller 50 receives the bitmap data BD for forminga wiring pattern by the droplet Fb, from the input/output device 51. Thecontroller 50 stores the bitmap data BD received from the input/outputdevice 51.

The controller 50 drives the Peltier element PT via the Peltier elementdriving circuit 56 so as to cool the metal ink F in the ink pack 33housed in the pack storage 16 down to 5 degrees Celsius. The controller50 drives the circulation pump VPC via the circulation pump drivingcircuit 59 so as to pump up the cooling water W of the heat exchanger 40and allow the water W to go around. The metal ink F that is cooled downto 5 degrees Celsius is warmed by the heat exchange with the coolingwater W in the heat exchanger 40 so as to be supplied to the dischargehead 20. The controller 50 drives a suction pump VP via thenegative-pressure generation pump driving circuit 58 so as to adjust thenegative pressure in the pack storage 16, adjusting the supply quantityof the metal ink F.

Then the controller 50 drives the Y-axis motor MY via the Y-axis motordriving circuit 53 so as to start conveying the stage 13. Once thecontroller 50 starts conveying the stage 13, the controller 50 producesthe pattern forming control signal SI based on the bitmap data BD so asto output the pattern forming control signal SI and the driving voltageCOM to the head driving circuit 54. Namely, the controller 50 driveseach of the piezoelectric elements PZ via the head driving circuit 54 soas to discharge the droplet Fb from the nozzle N that is selected, everytime the desired forming position passes directly under the dischargehead 20.

In addition, the controller 50 produces the pattern forming controlsignal SIb based on the bitmap data BD so as to output the patternforming control signal SIb and the driving voltage COMb to the laserdriving circuit 60. The controller 50 drives each of the semiconductorlasers LS (each of the semiconductor lasers LS of the firstsemiconductor laser device LD1, in this case) via the laser drivingcircuit 60 so as to irradiate the droplet Fb with the laser light L fromthe semiconductor laser LS that is selected, every time the droplet Fbthat lands on the green sheet S passes through a position that is to beirradiated with the laser light L. The laser light L heats the dropletFb that lands on the green sheet S so as to dry the droplet Fbinstantly. Thus the desired wiring pattern is formed on the green sheetS.

Here, advantageous effects of the second embodiment will be describedbelow.

(4) According to the embodiment, the heat exchanger 40 carries out theheat exchange between the metal ink F that is cooled and the coolingwater W that is warmed so as to warm the metal ink F. Thus the heatexchanger 40 decreases the viscosity of the metal ink F, so that themetal ink F having low viscosity is supplied to the inside of thedischarge head 20. Accordingly, the clogging of the nozzle N of thedroplet discharge head 20 is prevented from occurring. Further, thedischarge quantity of the droplet Fb from the discharge head 20 can bestabilized, being able to form a pattern with high accuracy in size andshape.

(5) According to the embodiment, the cooling water W that is cooled bythe metal ink F goes around the first semiconductor laser device LD1 andthe second semiconductor laser device LD2 to be warmed again by wasteheat from each of the semiconductor lasers LS and the circuit elements.Namely, the embodiment does not need a heating means for merely heatingthe metal ink F or the cooling water W. Thus the droplet dischargingdevice 10 can achieve energy-saving. In addition, since the number ofcomponents can be decreased, the droplet discharging device 10 can beformed small in size (achieve space saving). Thus the dropletdischarging device 10 can achieve natural resource saving, namely befriendly to the environment.

(6) In addition, in the first semiconductor laser device LD1 and thesecond semiconductor laser device LD2, each of the semiconductor lasersLS and the circuit elements is cooled by the cooling water W, being ableto suppress fluctuation of the operation property due to the heatgeneration thereof. Further, the droplet discharging device 10 does notneed the cooling means for merely cooling the cooling water W, beingable to achieve energy-saving. In addition, since the number ofcomponents can be decreased, the droplet discharging device 10 can beformed small in size (achieve space saving). Thus the dropletdischarging device 10 can achieve natural resource saving, namely befriendly to the environment.

(7) According to the embodiment, the supply tube T includes thestainless pipe Ta having high heat conductivity at the inside of theheat exchanger 40. Therefore, the heat exchanger 40 can improve theefficiency of the heat exchange between the metal ink F that is cooledand the cooling water W that is warmed.

(8) According to the embodiment, the cooling water W is cooled by thecooling mechanism of the circulation pump VPC as well as by the heatexchanger 40. Therefore, each of the semiconductor lasers LS and thecircuit elements of the first semiconductor laser device LD1 and thesecond semiconductor laser device LD2 can be cooled with higher coolingeffect.

The above-mentioned embodiments may be changed as the following.

In the first embodiment, the blower 34 can be omitted. Namely, thesupply tube T may be attached directly to the heat generating part PTbof the Peltier element PT. Accordingly, the supply tube T (the metal inkF) can directly cool down the heat generating part PTb of the Peltierelement PT. In this case as well, one Peltier element PT can achievecooling the ink pack 33 (the metal ink F) housed in the pack storage 16and heating the metal ink F. Thus the droplet discharging device 10effectively uses the heat generated from the Peltier element PT so thatthe droplet discharging device 10 can include fewer components andachieve energy-saving, namely be friendly to the environment. In a word,it is enough that the supply tube T thermally contacts with the heatgenerating part PTb of the Peltier element PT.

In the first embodiment, the supply tube T contacts the blower 34. Asshown in FIG. 10, the supply tube T may be multiply-wound around theouter walls of the heat insulating material 31 of the pack storage 16.At this time, it is preferable that the upstream side of the supply tubeT be disposed at the inner winding and the downstream side of the supplytube T be disposed at the outer winding.

Thus, this structure can increase the distance that the metal ink Fflows from the pack storage 16 to the discharge head 20 through thesupply tube T, namely the chance of heating the metal ink F by the air Ais increased. Thus the droplet discharging device 10 can save the energythat is needed to warm the metal ink F.

In addition, the supply tube T is wound such that the upstream sidethereof is disposed at the inner winding of the whole supply tube T andthe downstream side thereof is disposed at the outer winding.Accordingly, the supply tube T can improve the heat insulating effect ofthe pack storage 16 with respect to the external air.

Further, the supply tube T is wound around the pack storage 16, so thatthe droplet discharging device 10 can be formed small in size, that is,formed in space saving shape.

In the first embodiment, the Peltier element PT cools down the ink pack33 (the metal ink F) housed in the pack storage 16 and heats the metalink F supplied through the supply tube T to the discharge head 20.However, a heat pump may be used as substitute for the Peltier elementPT in the droplet discharging device 10.

At this time, a cool side (cooling part) of the heat pump cools down theink pack 33 (the metal ink F) in the pack storage 16, and a warm side(heat generating part) thereof warms the metal ink F that is to besupplied to the discharge head 20. Here, the warm side of the heat pumpmay warm the green sheet S at the same time.

While the droplet discharging device 10 includes one droplet dischargehead 20 in the first embodiment, the number of the droplet dischargehead 20 is not limited. The droplet discharging device 10 may include aplurality of droplet discharge heads 20. In this case, as shown in FIG.11, the pack storage 16 houses a plurality of ink packs 33 for theplurality of discharge heads 20. Each of supply tubes T coupling each ofthe ink packs 33 and the each of the discharge heads 20 ismultiply-wound around the outer walls of the heat insulating material 31of the pack storage 16. When the supply tubes T is multiply-wound, thesupply tubes T may be wound such that the upstream sides of the supplytubes T are disposed at the inner winding and the downstream sides ofthe supply tubes T are disposed at the outer winding.

In the first embodiment, the blower 34 warms the meal ink F flowing inthe supply tube T by the heat exchange between surrounding warm air andthe metal ink F. However, the blower 34 may warm the metal ink F byintroducing remaining heat (waste heat) of the rubber heater H to thesupply tube T.

In the second embodiment, the circulation pump VPC has the coolingmechanism, but it may be omitted. Namely, it is enough that the coolingwater W is cooled merely by the heat exchanger 40. In this case, thecirculation pump VPC does not include the cooling mechanism, so that thedroplet discharging device 10 includes fewer components and can achieveenergy-saving, namely be friendly to the environment.

In the second embodiment, the cooling water W circulates so as to warmthe metal ink F and cool each of the semiconductor lasers LS and thecircuit elements. However, as shown in FIG. 12, each of the cases K ofthe first semiconductor laser device LD1 and the second semiconductorlaser device LD2 may include a cooling fan 70. In particular, thecooling fan 70 may exhaust warm air of the inside of the case K andintroduce cool external air into the case K correspondingly to theexhaustion, thus cooling each of the semiconductor lasers LS and thecircuit elements. Then the cooling fan 70 may blow the warm air (hotair) that is exhausted from the case K to the stainless pipe Ta of thesupply tube T.

In such structure as well, the droplet discharging device 10 can warmthe metal ink F by using waste heat from each of the semiconductorlasers LS and the circuit elements. Thus, the droplet discharging device10 does not need any special heating means for merely heating the metalink F, so that the droplet discharging device 10 can include fewercomponents and achieve energy-saving, namely be friendly to theenvironment.

In the second embodiment, the Peltier element PT cools the metal ink F.However, other cooling means may be used to cool the metal ink F.

In the second embodiment, the droplet discharging device 10 includes twodischarge heads 20. However, the droplet discharging device 10 mayinclude one or more than two droplet discharge heads 20.

In the second embodiment, the first semiconductor laser device LD1 andthe second semiconductor laser device LD2 serve as a light source.However, LED may be used as the light source and light emitted from theLED may be used.

In the above embodiments, the suction pump VP adjusts the inner pressureof the pack storage 16. However, the pack storage 16 may include aself-sealing valve so as to adjust the inner pressure of the packstorage 16 by using it.

While the functional liquid is the metal ink F in the above embodiments,it is not limited. Any functional liquid that needs to be maintained atlow temperature may be used. The temperature for maintenance may bechanged appropriately depending on the functional liquid.

In the above embodiments, the droplet discharging device 10 forms thewiring pattern on the green sheet S. However, the droplet dischargingdevice 10 may form the pattern on a substrate made of glass or the like.

In the above embodiments, the droplet discharge means is the dropletdischarge head 20 of the piezoelectric element drive system. However,the droplet discharge head may be the one of a resistance heating systemor of an electrostatic driving system.

1. A method for heating a functional liquid of a droplet dischargingdevice, having: a storage that houses a container storing a functionalliquid containing a functional material; a droplet discharge headdischarging the functional liquid in a droplet; a cooling means includedto the storage and cooling the functional liquid; and a supply tubesupplying the functional liquid that is cooled in the storage to thedroplet discharge head, the method comprising: heating the functionalliquid in the supply tube with waste heat that is generatedcorrespondingly to irradiation of the light source.
 2. A dropletdischarging device, comprising: a storage that houses a containerstoring a functional liquid containing a functional material; a dropletdischarge head discharging the functional liquid in a droplet to anobject; a cooling means cooling the functional liquid that is stored inthe container housed in the storage; a supply tube provided between thecontainer and the droplet discharge head and supplying the functionalliquid stored in the container to the droplet discharge head; a lightsource irradiating an area of the object on which the droplet lands withlight; and a heating means heating the supply tube with waste heat thatis generated correspondingly to irradiation of the light source.
 3. Thedroplet discharging device according to claim 1, wherein the heatingmeans includes a circulation pump and a heat exchanger; the circulationpump allows a refrigerant to circulate between a case of the lightsource and the heat exchanger; and the heat exchanger provides heat ofthe case to the functional liquid that is in the supply tube by heatexchange between the refrigerant and the supply tube.
 4. The dropletdischarging device according to claim 3, wherein the circulation pumpincludes a cooling mechanism and circulates the refrigerant that iscooled with the cooling mechanism to the case of the light source. 5.The droplet discharging device according to claim 1, wherein the heatingmeans is a cooling fan that sucks external air to an inside of the caseof the light source and blows inner air of the case to the supply tubethat is provided outside of the case.